The present invention relates to a circuit breaker and more particularly to a fail-safe electronic circuit breaker that becomes permanently disabled if a simulated circuit fault is not detected within a predetermined amount of time.
Typically, electrical appliances receive alternating current (AC) power from a power source. The electric appliance receives current from the power source via an electrical outlet that is connected to a plurality of electrical conductors to create an electrical circuit. The plurality of electrical conductors generally includes at least a line conductor and neutral conductor.
The connection of the electrical appliance to the power source can present some problematic conditions. For example, a ground fault condition may occur in the electrical conductors and/or the electrical circuit. A ground fault condition exists when there is an imbalance between the current flowing between the line conductor and the neutral conductor. In addition, an arc fault condition may occur in the electrical conductors and/or the electrical circuit. An arc fault condition is an intermittent high impedance fault that is caused, for example, by worn insulation, loose connections and broken conductors.
These circuit faults can present problematic conditions to, for example the appliance, user, and repair personnel. Therefore, circuit breakers have been developed that use sophisticated electronic circuitry to detect the various circuit fault conditions and to interrupt current flowing through the electrical conductors when the circuit fault is detected. To improve the reliability of the circuit breaker, test circuits are provided that can be used to test the circuit breaker to determine the functionality of electronic circuitry and tripping mechanism of the circuit breaker. The test circuit simulates various fault conditions that should be detected by the circuit breaker.
The test circuit provides an important benefit to the appliance, users and repair personnel and ensures that the entire electronic circuitry of the circuit breaker is functioning properly to detect various circuit fault conditions. A circuit breaker that fails to detect a simulated circuit fault from a test circuit is also likely to fail to detect actual circuit faults that may be present in the conductors and/or the circuit comprising the appliance connected to the power source. Therefore, in the event that a circuit breaker fails to detect a simulated fault from the test circuit, the circuit breaker should be replaced or rendered non-functional. As discussed above, failure to detect any or all circuit faults presents problematic conditions for the appliance, the user and repair personnel. Therefore, it is desired that a circuit breaker be produced that is rendered non-functional if the circuit breaker fails to detect a simulated circuit fault produced by a test circuit.
In one exemplary embodiment of the present invention, a fail-safe electronic circuit breaker is provided that has a test circuit connected to a fault detection circuit. The test circuit selectively generates a simulated circuit fault. The fail-safe electronic circuit breaker also includes a trip mechanism connected to the fault detection circuit. The trip mechanism includes a trip lever connected to the fault detection circuit for tripping the fail-safe electronic circuit breaker when the fault detection circuit detects a circuit fault. In addition, a test-error mechanism is provided and is connected to the test circuit. The test-error mechanism has at least a first position and a second position. The test-error mechanism comprises a fusible link that is connected to the test circuit. The fusible link retains a first end and a second end of the test-error mechanism in the first position. The fusible link liquefies when the fault detection circuit fails to detect the simulated circuit fault after about the predetermined amount of time. The test-error mechanism also includes a bias member that is positioned between the first end and the second end. In a representative embodiment, the bias member comprises a spring that is in a state of compression with respect to a relaxed state.
The bias member places the test-error mechanism in the second position when the fusible link is liquefied. When in the second position, the test-error mechanism contacts the trip lever and after causing the fail-safe electronic circuit breaker to trip, permanently disables the fail-safe electronic circuit breaker when the test-error mechanism is in the second position.
In another exemplary embodiment, a fail-safe electronic circuit breaker is provided that has a test circuit connected to a fault detection circuit. The test circuit selectively generates a simulated circuit fault. The fail-safe electronic circuit breaker also includes a trip mechanism connected to the fault detection circuit. The trip mechanism trips the fail-safe electronic circuit breaker when the fault detection circuit detects a circuit fault. A test-error mechanism is connected to the test circuit. The test-error mechanism has at least a first position and a second position. In addition, the test-error mechanism includes a fusible link that is connected to the test circuit. The fusible link retains a first end and a second end of the test-error mechanism in the first position. The fusible link liquefies when the fault detection circuit fails to detect the simulated fault after about the predetermined amount of time. A bias member is positioned between the first end and the second end. The bias member places the test-error mechanism in the second position when the fusible link is liquefied. In addition, a heating element is connected to a power source and emits heat when the test-error mechanism is in the second position. A bimetallic strip is positioned proximate to the heating element. The bimetallic strip has at least a first state and a second state, and the bi-metallic strip enters the second state after being heated by the heating element. When in the second state, the bi-metallic strip causes the trip mechanism to trip the fail-safe electronic circuit breaker.